The present invention relates to an information-outputting apparatus such as a monitor apparatus connected to a network connected to a plurality of electronic apparatuses through digital buses each conforming to typically the IEEE 1394 standard, an information-reporting method for informing the user of information on a content to be output by the information-outputting apparatus and an information-signal-supply-route-selecting method in the network.
In recent years, a variety of digital contents are abundantly provided by way of communication media such as broadcasting media and the Internet as well as through recording media such as a DVD (digital video disc). It is conceivably possible to widen the range of applications of such abundantly available digital contents and to well provide an environment of utilizing digital contents wherein the user has a high degree of freedom to use the contents.
It is also conceivably possible to provide a digital interface to each of a variety of digital apparatuses such as digital-content playback and recording apparatuses. By providing a digital interface to each of a variety of digital apparatuses as such, a digital content can be transmitted at a high speed and copied as well as played back without degrading the quality.
While there are a variety of digital interfaces, a digital interface conforming to the IEEE 1394 standard draws much attention. The IEEE 1394 digital interface is capable of transmitting a digital content at a high speed and protecting a copyright of a digital content with a high degree of reliability. To be more specific, the digital interface conforming to the IEEE 1394 standard is capable of transmitting signals such as digital video and audio signals, which must satisfy real-time requirements.
In addition, in a communication through a digital interface conforming to the IEEE 1394 standard between an electronic apparatus serving of a source of a digital content and an electronic apparatus serving as a recipient of the digital content, by adding information on copy control to the digital content, the apparatus transmitting the digital content is capable of determining whether or not to give the recipient apparatus a right to copy the digital content.
The electronic apparatus serving of a source of a digital content encrypts the digital content to be transmitted. If the electronic apparatus serving as a recipient of a digital content is treated as an apparatus not allowed to copy the digital content by adding information on copy control to the digital content, the recipient apparatus is not informed of an encryption key information for decrypting the encrypted digital content so that a copyright of the digital content can be protected with a high degree of reliability.
By the way, digital television broadcasting presenting digital contents through broadcasting media is already under way. It is thus conceivably possible to provide a digital monitor apparatus or a digital television receiver that has a function for receiving a digital television broadcast. In the digital television broadcasting, digital data is typically data comprising a plurality of broadcasted programs. Prior to broadcasting, the data is subjected to compression adopting an MPEG method and multiplexing. Thus, the digital monitor apparatus must have an MPEG decoder.
By providing a digital interface to a digital monitor apparatus having an MPEG decoder, a digital content completing an encoding process adopting the MPEG method can be supplied to the apparatus as it is. The digital monitor apparatus is capable of decoding and playing back the digital content. Thus, a digital interface provided to a digital monitor apparatus is conceivable.
By merely providing a digital monitor apparatus with a digital interface, however, a problem arises in some cases. That is to say, while a digital monitor apparatus having a digital interface can be connected to a digital VTR, a hard-disc drive and the so-called camcoder, which is equipment comprising a video camera and a VTR built into a single body, a video signal stored in a recording medium such as a video tape by a digital VTR or a camcoder is in some cases a DV (Digital Video) signal obtained as a result of data compression based on a DV method instead of a signal encoded by adopting the MPEG method.
The DV method is a home digital VTR standard set by an HD Digital Conference, which was established by such as manufacturers of digital equipment as promoters. In accordance with the DV method, a DV signal is obtained as a result of compressing data of a video signal in frame units. That is to say, a DV signal consists of only I (Intra) picture components in the so-called MPEG method. An I picture is a picture obtained as a result of a intra-frame encoding process.
Thus, a digital monitor apparatus having only an MPEG decoder is not capable of decoding and playing back a DV signal supplied thereto by a digital VTR or the so-called camcoder by way of the digital interface.
Assuming that a digital monitor apparatus 1 having an analog input terminal in addition to an MPEG decoder and a digital interface is connected to a DV storage 2 of typically a digital VTR, an MPEG-TS (Transport Stream) storage 3 of typically a hard disc and a DV camcoder 4 as shown in FIG. 1.
In FIG. 1, solid lines 5, 6 and 7 each represent a digital signal cable whereas dashed lines 8, 9 and 10 each represent an analog signal cable. That is to say, the digital monitor apparatus 1 is connected to the DV storage 2, the MPEG-TS storage 3 and the DV camcoder 4 by the analog signal cables 8, 9 and 10 respectively and to the DV storage 2 by the digital signal cable 5, whereas the DV storage 2 is connected by the digital signal cable 6 to the MPEG-TS storage 3 which is connected to the DV camcoder 4 by the digital signal cable 7 to form a network.
It should be noted that the MPEG-TS storage 3 is an apparatus used for, among others, storing and playing back an MPEG-TS signal, which is obtained as a result of a process of multiplexing digital contents each resulting from data compression adopting the MPEG method.
A content decoded by the DV storage 2, the MPEG-TS storage 3 or the DV camcoder 4 into an analog signal is supplied to the digital monitor apparatus 1 through the analog signal cable 8, 9 or 10 respectively. In this case, the video of the content is displayed on a screen G of the digital monitor apparatus 1 as shown in FIG. 2A and the sound of the content is output by speakers SP1 and SP2 as is the case with the conventional apparatus.
By the same token, an MPEG-TS signal can be supplied from the MPEG-TS storage 3 to the digital monitor apparatus 1 through the digital signal cables 6 and 5 as it is. In this case, since the digital monitor apparatus 1 has an MPEG decoder, the monitor apparatus 1 is capable of displaying the video of the digital content on the screen G thereof as shown in FIG. 2A and outputting the sound of the content through the speakers SP1 and SP2.
By the same token, a DV signal can be supplied to the digital monitor apparatus 1 from the DV storage 2 through the digital signal cable 5 or from the DV camcoder 4 through the digital signal cables 7, 6 and 5 as it is. In this case, however, since the digital monitor apparatus 1 does not have a DV decoder, the monitor apparatus 1 is not capable of playing back the DV signal. As a result, as a conceivable method, the digital monitor apparatus 1 is put in a mute state as typically shown in FIG. 2B to prevent the video and the sound of the digital content from being output as noises.
With such a method, however, the user is not capable of immediately knowing why the content the user is trying to watch and listen to is not played back. In addition, in the case of a network comprising a plurality of electronic apparatuses connected to each other as shown in FIG. 1, the user of the digital monitor apparatus 1 is not capable of recognizing which route is used for supplying a content to the monitor apparatus 1 from an external apparatus connected to the monitor apparatus 1 by the network.
In the case of the network shown in FIG. 1, for example, as described above, the digital monitor apparatus 1 serving as the core apparatus may receive 3 different kinds of contents, namely:                (1) a decodable and reproducible digital content;        (2) an undecodable digital content; and        (3) a content supplied as an analog signal.        
If an undecodable digital content is inadvertently supplied to the digital monitor apparatus 1, there may be raised a problem that the undecodable digital content is interpreted incorrectly as a failure occurring in the monitor apparatus 1 or the apparatus generating the content. In addition, since a content may be supplied to the digital monitor apparatus 1 from the same electronic apparatus through an analog signal cable or a digital signal cable, it is difficult to handle contents in the information reporting and outputting system in some cases. Thus, the environment for utilizing a digital content cannot be said to be sufficiently well provided yet.